At Marineland, we design our filter cartridges to meet the absolute highest standards of water purification performance and operational ease. Each preassembled cartridge slides easily into place, providing superior mechanical and chemical filtration and making replacement fast, dry, and effortless. The cartridge mechanically filters water through a pad of double thick poly-fiber. Debris and waste particles are trapped, and water is chemically filtered through Marineland's Black Diamond Premium Activated Carbon.Black Diamond is made from bituminous coal, heated to 1800 degrees to ensure adsorptive efficacy. Each granule contains millions of microscopic pores of various sizes that chemically attract and remove harmful dissolved pollutants from the water. Our super-efficient carbon keeps working long after most carbons stop . . . and it's absolutely phosphate free. Inside the cartridge, a patented ribbed backing ensures the even distribution of activated carbon to deliver maximum water-to-carbon contact. There is no tea bag effect, no water bypass as with loose or bagged methods. The result? Crystal clear, crystal clean water.There's a Rite-Size Cartridge for every Penguin Filter . . . and for other filters as well. The heavy-duty Emperor Filter Cartridge delivers superior activated carbon filtration and 45% more mechanical filter area. The custom Eclipse Filter Cartridge is designed specifically for horizontal placement in our extensive selection of Eclipse systems. And our new color-coded packaging ensures fool-proof cartridge selection.